Low insertion loss optical beam steerer

Details Low insertion loss optical beam steerer Low insertion loss optical beam steerer

1991-01-18

1992-04-21

Hille, Rolf

Optical: systems and elements

Holographic system or element

Using a hologram as an optical element

359 36, 359 70, 359 95, G02F 113

Patent

active

051073579

ABSTRACT:
An optical beam scanner or spoiler includes an array of electrically controlled liquid crystal phase shifters. Each element of the phase shifter includes an active region where proper phase shift occurs, and also includes another region, generally near the edges of the element, in which light transmission does not occur or in which improper modulation results. The inefficient regions reduce the light transmission or modulation efficiency of the array. An aperture illuminator includes a Talbot plane phase plate (also known as a Fresnel image phase plate) interposed between the incident light beam and the liquid crystal array. The phase plate includes a transparent substrate with a binary pattern of regions of relatively higher and lower index of refraction in a repeating pattern with a period P. In a particular embodiment of the invention, the regions are physically raised and lowered portions of a surface. The phase plate generates an interference pattern of energy maxima and minima, and is located so the maxima fall on the active regions of the liquid crystal array, and the minima on the inactive portions. A second phase plate similar to the first (or a second pass through the first phase plate in a reflective system) reduces the magnitude of far-field grating lobes created by the first phase plate.

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"Efficient Array Illuminator Using Binary-Optics Phase Plates at Fractional-Talbot Planes" by Leger et al., Published at pp. 288-290 of Optics Letters, vol. 15, No. 5, Mar. 1, 1990.
"Making An Array Illuminator Based On The Talbot Effect", by Lohmann et al., Published at p. 4337 of the Oct. 10, 1990 Issue, vol. 29, No. 29 of Applied Optics.
"Optical Beam Steering Using A Multichannel Lithium Tantalate Crystal" by Meyer, Published at p. 613 et seq. Mar. 1972, vol. 11, No. 3 of Applied Optics.
"Continuous Wide Angle Beam Steering Using Translation of Binary Microlens Arrays and a Liquid Crystal Phased Array" by Flood et al., was Published SPIE 1211, Jan. 1990.
"Phase Control of Coherent Diode Laser Arrays Using Liquid Crystals", by Cassarly et al., was Published SPIE 1043, Jan. 1989.
"Self-Imaging Cavities for Phase Locking of Laser Diode Arrays and Fill Factor Enhancement", by D'Amato et al., Published in the Friday Afternoon, Apr. 28, 1989 CLEO Proceedings.

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